Composition for forming a coating type BPSG film, substrate, and patterning process

A composition for forming a BPSG film, comprising:

• one or more silicic acid skeletal structures represented by the formula (1);
• one or more phosphoric acid skeletal structures represented by the formula (2);
• one or more boric acid skeletal structures represented by the formula (3);
• and one or more silicon skeletal structures represented by the formula (4);
• wherein the composition contains a polysilane structure obtained by a coupling between units in the formula (4),
• wherein R1, R2, R3, R4, R5, R6, R7, and R8 each represent a hydrogen atom or an organic group having 1 to 30 carbon atoms, wherein a hydrogen atom(s) in the organic group may be substituted by a halogen atom(s);
• R9, R10, R11, R12, R13, and R14 each represent a methyl group, a phenyl group, or a hydroxyl group;
• m10, m11, m12, and m13 each represent a molar fraction in the silicic acid skeletal structure, and satisfy m10+m11+m12+m13=1, 0≦m10≦0.3, 0≦m11≦0.5, 0≦m12≦0.7, and 0<m13≦1;
• m20, m21, and m22 each represent a molar fraction in the phosphoric acid skeletal structure, and satisfy m20+m21+m22=1, 0≦m20≦1, 0≦m21≦1, and 0≦m22<1;
• m30 and m31 each represent a molar fraction in the boric acid skeletal structure, and satisfy m30+m31=1, 0≦m30≦1, and 0≦m31≦1;
• and m40, m41, m42, and m43 each represent a molar fraction in the silicon skeletal structure, and satisfy m40+m41+m42+m43=1, 0≦m40≦1, 0≦m41≦1, 0≦m42≦1, and 0≦m43≦1.